This invention relates to machine for forming, filling, and sealing reclosable bags from a continuous web of bag material, and more particularly to a steering, joining and guiding mechanism for such a forming, filling, and sealing machine.
Bags of various types have been used for packaging a wide variety of products. For example, cereals, cookies, and potato chips are often packaged in bags. These bags can serve as the external packaging for the products, or can be inserted into boxes as a liner for the boxes. When packaging perishable materials such as cereal, cookies, and potato chips, the bags should be sealed, as sealed bags help to preserve the product contained therein by preventing the co-mingling of outside air and moisture with the product in the bags.
Conventional sealed bags (such as most cereal bags and potato chip bags) have seals which are formed by gluing together or heat sealing together a pair of opposed edges of the bags. One problem with such conventional sealed bags is that they cannot be resealed after being opened. Thus, once the bag is opened, the user cannot prevent the unwanted intrusion of outside air and moisture into the bag.
Reclosable bags are known. Usually, reclosable bags include a pair of fastener elements (such as a pair of rib and groove profiles or "zippers"), which the user fastens together after opening to thereby effectively seal the contents of the bag from the intrusion of unwanted air and moisture. One example of such a reclosable bag is the ZIPLOC.RTM. brand food storage bag manufactured by the Dow Chemical Company, the assignee of the instant application.
Both conventional and reclosable bags share a common feature in that they are usually formed from a continuous roll (web) of bag film. This bag film web is filled with the product (such as cereal) and the web is subdivided into a plurality of individual bags.
Machines for forming and filling bags from a continuous web of bag material are known.
Toss, U.S. Pat. No. 3,815,317 relates to an apparatus for forming, filling and sealing zippered plastic bags. A continuous bag film web is provided on a roll with the rib and groove profiles interlocked. The profiles are opened and the film spread out to remove any wrinkles or folds from the web. The film is then folded and the profiles are reengaged. The web is then cross-sealed, filled with the product through the remaining open side, and that open side is sealed to form the final bag assembly. In the Toss apparatus a pin unlocks the interlocked profiles. A guide device holds the profiles apart. The guide device includes guide wheels which engage the edges of the film. The profiles are reengaged through the use of closure rolls.
Tillman, U.S. Pat. No. 4,355,494 relates to a machine for making reclosable bags. The Tillman device is not a true form, fill and seal machine but rather a forming machine only. Tillman forms zippered bags by applying the rib and groove profiles to a traveling web. The bag film is then formed into a tube over a forming shoulder. The rib and groove profiles are joined by a guide means which is best shown in detail in FIGS. 4 and 5 of the Tillman patent. Tillman's guide means includes multiple roller pairs which are utilized to guide the profiles into engagement between a pair of press rolls.
Maxfield, U.S. Pat. No. 2,146,308, relates to a vertical form, fill and seal operation. A plastic film web is formed around a tube and then a capping strip is applied over the edges of the tube. This capping strip is positioned by a pair of heated rollers. The tube is filled and then laterally sealed and severed to produce the packaged product. The Maxfield device does not utilize zippered bag film. Rather, Maxfield utilizes a capped bag.
Pike, U.S. Pat. No. 3,807,118 also relates to a non-zippered form, fill and seal system. In the Pike device, a heat sealable minor web is applied to one edge of the web. A tear element is applied to the opposite edges. The two edges are aligned and heat sealed as part of the formation of the bag.
One difficulty encountered in both conventional and reclosable bag forming, filling, and sealing operations is maintaining the bag film from which the bags are cut in a proper alignment as the bag film travels through the forming, filling and sealing machine. This problem is especially acute in the forming, filling, and sealing of zipper-type reclosable bags, because the zipper halves need to be aligned properly in order to be closed properly.
It is therefore an object of this invention to provide an improved zipper closure and bag film aligning means for a packaging machine.